When Apple first introduced the Apple Watch back in September of 2014, there were already some third-party apps running on it. When Apple re-introduces the Apple Watch during Monday's Spring forward event event, there will no doubt be many more.
Just like with the iPhone and iPad, Apple grants some developers early access so that they can have apps ready to show off on the keynote stage, and polished for launch when the App Store goes live. Unlike the iPad, which was chained to tables and locked into windowless rooms, the Apple Watch isn't going to developers — developers are coming to Apple's labs. Bloomberg details some of the security involved:
Internet access is blocked inside the rooms, and no outside materials can be brought in to the labs with the test watches, a person who attended said. The companies, sometimes sharing a room, must bring in source code for their apps on a computer hard drive that can't leave Apple's headquarters. To prevent information from leaking out, Apple is storing the code and sending it to the companies closer to the watch's introduction date, the person said.
It's under non-disclosure agreement (NDA, but the developers are going to Cupertino, repeatedly, so it's also not exactly the secret it's being made out to be. Apple simply doesn't like their surprises being spoiled by anyone outside of Apple
No doubt we'll see a lot more come Monday.